DESCRIPTION: (Applicant's Abstract) Microbial keratitis is a common, economically important ocular disease that, despite the availability of antimicrobial therapy, can reduce vision and the quality of life. A major unresolved issue is the role of the microbiology laboratory in guiding decision-making. The goal of this pilot research is to use clinical and microbiologic data from patients who have had microbial corneal infection to determine how antimicrobial resistance affects outcome. Using a retrospective cohort study design, this epidemiological investigation will examine the effect of the appropriateness of initial antibiotic therapy and the in vitro susceptibility profile of corneal isolates on vision, length of antibiotic treatment, and ocular complications requiring surgery. Multivariable logistic-regression and proportional-hazards analyses will control for potential confounders (including demographic variables, disease duration, severity parameters, and adjunctive therapy) and will consider possible effect modifiers (such as microbial taxonomy and minimal inhibitory concentration) to determine adjusted relative effect measures. The knowledge derived from this research has a potentially high impact on vision research and on clinical practice and has the potential to direct broader investigations into the problem of antimicrobial resistance and the optimal use of antibiotics in ophthalmology.